全文获取类型
收费全文 | 154621篇 |
免费 | 8424篇 |
国内免费 | 78篇 |
专业分类
林业 | 6313篇 |
农学 | 5223篇 |
基础科学 | 986篇 |
20472篇 | |
综合类 | 21735篇 |
农作物 | 5938篇 |
水产渔业 | 7780篇 |
畜牧兽医 | 82496篇 |
园艺 | 2026篇 |
植物保护 | 10154篇 |
出版年
2020年 | 1331篇 |
2019年 | 1606篇 |
2018年 | 2546篇 |
2017年 | 2854篇 |
2016年 | 2598篇 |
2015年 | 2179篇 |
2014年 | 2772篇 |
2013年 | 6607篇 |
2012年 | 4835篇 |
2011年 | 5817篇 |
2010年 | 3988篇 |
2009年 | 3980篇 |
2008年 | 5759篇 |
2007年 | 5565篇 |
2006年 | 5160篇 |
2005年 | 4695篇 |
2004年 | 4516篇 |
2003年 | 4569篇 |
2002年 | 4158篇 |
2001年 | 5166篇 |
2000年 | 5049篇 |
1999年 | 4049篇 |
1998年 | 1629篇 |
1997年 | 1595篇 |
1996年 | 1482篇 |
1995年 | 1764篇 |
1994年 | 1477篇 |
1993年 | 1503篇 |
1992年 | 3001篇 |
1991年 | 3167篇 |
1990年 | 3171篇 |
1989年 | 3169篇 |
1988年 | 2846篇 |
1987年 | 2824篇 |
1986年 | 2784篇 |
1985年 | 2622篇 |
1984年 | 2187篇 |
1983年 | 1929篇 |
1979年 | 1998篇 |
1978年 | 1529篇 |
1977年 | 1361篇 |
1976年 | 1385篇 |
1975年 | 1460篇 |
1974年 | 1677篇 |
1973年 | 1766篇 |
1972年 | 1649篇 |
1971年 | 1430篇 |
1970年 | 1498篇 |
1969年 | 1450篇 |
1967年 | 1300篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Protection of animals against respiratory infections has long been known to depend on respiratory mucosal immunity. However, few studies have been reported on the immune response following intranasal (i.n.) immunisation with non-living, soluble antigens. This study determined the kinetics of the humoral and cellular immune responses in calves after i.n. immunisation with Limulus haemocyanin (LH) with cholera toxin adjuvant, or subcutaneous (s.c.) immunisation with LH in incomplete Freund's adjuvant. A proliferative response of peripheral blood mononuclear cells cultured in vitro with LH was observed in animals immunised 7-10 days after i.n. and s.c. immunisations with no significant differences between the two immunised groups. LH -specific antibody was present in the serum of animals immunised s.c. (IgM, IgG1 and IgG2) and i.n. (IgA). Although significant IgA responses were observed, i.n. immunisations in cattle with soluble protein antigens and cholera toxin as an adjuvant did not induce a strong systemic immune response. 相似文献
992.
A four-month-old male Labrador retriever was presented for polyuria, polydipsia and persistent euglycaemic glucosuria. On referral, diagnostic tests demonstrated abnormal fractional excretions of electrolytes, increased urinary excretion of selected amino acids, mild renal tubular acidosis and mild proteinuria, indicating renal tubular dysfunction. Pyelonephritis was suspected and potentiated amoxycillin was administered. On re-evaluation at six months of age, the dog was no longer polyuric or polydipsic and the metabolic abnormalities associated with the tubulopathy had resolved. Transient Fanconi's syndrome has not previously been reported in small animals. This report demonstrates the potential for recovery of function in cases presenting with renal tubulopathies. 相似文献
993.
Chicken leptin: properties and actions 总被引:6,自引:0,他引:6
Taouis M Dridi S Cassy S Benomar Y Raver N Rideau N Picard M Williams J Gertler A 《Domestic animal endocrinology》2001,21(4):319-327
Chicken leptin cDNA shows a high homology to mammalian homologous, with an expression localized in the liver and adipose tissue. It is noteworthy, that the hepatic expression is most likely associated with the primary role that this organ plays in lipogenic activity in avian species. As in mammals, chicken leptin expression is regulated by hormonal and nutritional status. This regulation is tissue-specific and with a high sensitivity in the liver compared to adipose tissue. The blood leptin levels are regulated by the nutritional state with high levels in the fed state compared to the fasted state. The recombinant chicken leptin markedly inhibits food intake as reported in mammals, suggesting the presence of an hypothalamic leptin receptor. The chicken leptin receptor has been identified and all functional motifs are highly conserved compared to mammalian homologous. Chicken leptin receptor is expressed in the hypothalamus but also in other tissues such as pancreas, where leptin inhibits insulin secretion and thus may have a key role in regulating nutrient utilization in this species. 相似文献
994.
995.
One hundred and five donkeys were examined over a 12-month period for the presence of Gasterophilus spp. larvae in their stomachs. G. intestinalis and G. nasalis were found, but there was a distinct seasonal variation in their abundance. The numbers of second-stage larvae (L2) peaked during the early winter and early summer, but they were absent or at low levels during the early spring and early autumn. This suggests that there are two periods of adult fly activity (late autumn and late spring) for both G. nasalis and G. intestinalis. Third-stage larvae (L3) were found throughout the year, but the lowest levels were seen in the late summer and autumn. The parasites also had an aggregated distribution, which may be due to host selection by the fly. The numbers of larvae did not vary significantly with age, which may be due to a lack of acquired protective immunity or to tolerance after repeated exposure. 相似文献
996.
Demierre S Tipold A Griot-Wenk ME Welle M Vandevelde M Jaggy A 《The Veterinary record》2001,148(15):467-472
The data from 20 dogs with histopathologically confirmed granulomatous meningoencephalomyelitis were reviewed in an attempt to identify clinical signs and morphological and cellular parameters, particularly the infiltration of mast cells, which might be associated with the clinical course of the disease. Thirteen of the dogs had the acute form of the disease and seven had the chronic form. Young to middle-aged, small breed female dogs were over-represented. Central vestibular signs were observed in six of the dogs with the acute disease. Analyses of cerebrospinal fluid revealed moderate to severe pleocytosis and high protein concentrations in all cases. Histopathological investigations revealed disseminated perivascular cuffs, large confluent granulomata, tissue necrosis, infiltration with neutrophils and a large number of mitotic cells in the dogs with either of the clinical forms of the disease. Tryptase-positive mast cells were observed in all the cases, but there were significantly larger numbers in the dogs with the acute form. 相似文献
997.
OBJECTIVE: To evaluate the efficacy and tolerance of a treatment protocol for obsessive-compulsive disorder, separation anxiety and noise phobia in dogs. DESIGN: A study was undertaken to assess clinical responses in 24 dogs diagnosed with one or more of three behavioural disorders stated above to a treatment regimen that included clomipramine and behaviour modification. PROCEDURE: A detailed behavioural and clinical history was obtained for each dog. Obsessive-compulsive disorder was diagnosed in nine cases: primary presenting complaints were tail-chasing, shadow-chasing, circling and chewing; one case was diagnosed with concurrent separation anxiety. Separation anxiety was diagnosed in 14 cases: presenting complaints included destruction, vocalisation and escaping in the absence of the owner; four cases also exhibited noise phobia. The study also included one dog diagnosed with noise phobia only and another with inappropriate fear responses. Clomipramine was administered orally twice daily. The starting dose was 1 to 2 mg/kg bodyweight. The dose was increased incrementally to a maximum of 4 mg/kg if needed. A behaviour modification program was designed and the owner instructed on its implementation. Dogs continued medication for at least 1 month after clinical signs disappeared or were acceptably reduced, then withdrawal of medication was attempted by decreasing drug dosage at weekly intervals while behaviour modification continued. RESULTS: The presenting clinical sign was largely improved or disappeared in 16 dogs, 5 demonstrated slight to moderate improvement and the behaviour was unchanged in 3. Clomipramine withdrawal was attempted in nine cases: this was successful in five. CONCLUSION: Clomipramine was effective and well-tolerated in controlling signs of obsessive-compulsive disorder and/or separation anxiety and/or noise phobia in 16 of 24 assessable cases, when used in combination with behaviour modification, and improvement in clinical signs was noted in 5 others. 相似文献
998.
Clinical, biochemical, and molecular aspects of Glanzmann's thrombasthenia in humans and dogs 总被引:3,自引:0,他引:3
Glanzmann's thrombasthenia (GT) is an inherited, intrinsic platelet function defect that involves the platelet glycoprotein complex IIb-IIIa, also known as the fibrinogen receptor and the integrin alphaIIbbeta3. The defect was originally described by Dr. Glanzmann in humans in 1918 as a bleeding disorder that differed clinically from other known coagulopathies. Over the decades that followed, researchers determined the biochemical and molecular basis for the disease in humans. Otterhounds with thrombasthenic thrombopathia, described in the 1960s, were the only animal model that closely resembled the disease described in humans until 1996. At that time, a Great Pyrenees dog was identified with unequivocal clinical and biochemical features of Type I GT The cDNA encoding for glycoproteins IIb and IIIa were sequenced in normal dogs in 1999, allowing for identification of specific mutations causing Type I GT in both Otterhounds and Great Pyrenees dogs. Knowing the molecular basis for Type I GT in dogs as well as the cDNA sequences in normal dogs should enhance the understanding of structure/function relationships of the alphaIIbbeta3 integrin and provide an excellent animal model for studies aimed at correction of GT in humans. The following review focuses on the structure and function of this platelet receptor and reviews the molecular, biochemical, and clinical aspects of Glanzmann's thrombasthenia in humans and dogs. 相似文献
999.
Brommer H Sloet van Oldruitenborgh-Oosterbaan MM Kessels B 《The Veterinary quarterly》2001,23(2):92-95
Reference values for haematological and blood biochemical variables may vary per breed and are influenced by age and, to a certain extent, by rearing conditions. To investigate the influence of age and rearing conditions, these variables were measured in Dutch Warmblood foals from birth to 5 months of age. The foals were divided into three groups with different exercise regimens: 14 foals got boxrest with no exercise; 14 foals were kept in comparable boxes, but received daily exercise; and 15 foals were maintained on pasture with free exercise. Blood samples were collected each month and 36 haematological and biochemical variables were measured. The influence of age and rearing conditions was statistically evaluated. Significant age effects were found for all variables with the exception of band-shaped leucocytes, eosinophilic leucocytes, basophilic leucocytes, monocytes, platelets, pCO2, and sodium, potassium, calcium, magnesium, creatinine and creatine phosphokinase levels. Rearing conditions appeared to influence the haemoglobin, packed cell volume, pH, base excess, bicarbonate, chloride, urea, and alkaline phosphatase values. Most age-related differences can be explained by growth and differentiation-related processes that are specific for young animals. Differences due to the different rearing conditions can partly be explained by the higher metabolism and greater maturation of tissues in foals maintained on pasture with free exercise. Some other differences were minor and were probably of no clinical relevance. The conclusion is that haematological and blood biochemical variables in the Dutch Warmblood foal mainly depend on age, thus warranting the use of specific age-related reference values for foals of this breed. 相似文献
1000.
The function of the immune system was studied in 34 bitches affected by pyometra. The mean age of the animals was 8.1 +/- 2.8 years. Samples of peripheral blood were examined using a battery of immunological tests. Data obtained from four sets of animals, grouped according to the severity of their disease, were compared. Leucocytosis (neutrophilia and partial monocytosis) and lymphopenia were detected in 62 per cent and 35 per cent of the bitches, respectively. The increase in the number of leucocytes was higher in the severely affected bitches. Inhibition of mitogen-driven lymphocyte proliferation was the characteristic feature of the immunological profile in bitches affected by pyometra, and this corresponded with the impairment of the general state of health. Sera from bitches showing functional inhibition of lymphocytes suppressed the activity of lymphocytes isolated from normal dogs. Sera from bitches affected by pyometra also had higher levels of immunoglobulins, lysozyme and circulating immune complexes. It can be concluded that pyometra is associated with an inflammatory response, but also with a marked suppression of immune system activity. 相似文献